1. Field of the Invention
The present invention relates to a battery module. More particularly, the present invention relates to a battery module suitable for a secondary battery and including a plurality of unit batteries in which cell barriers disposed in the unit batteries have different characteristics depending on their position in the battery module.
2. Description of the Related Art
As generally understood in the art, a primary battery is a single use battery. In contrast, a secondary battery, commonly known as a rechargeable battery, may be repeatedly discharged and recharged. Secondary batteries are generally classified into different types based on the external shape of the secondary battery. Common secondary battery types include prismatic, e.g., square, and cylindrical batteries. Low power batteries may be used for various portable electronic devices, e.g., cellular phones, laptop computers, camcorders, etc. Larger, bulk size batteries may be used as a power source for drive motor, e.g., as used in hybrid electric vehicles (HEVs).
In order to be used for high power or high capacity applications, e.g., drive motors, HEVs, etc., multiple batteries may be assembled in the form of a battery module. The battery module may be formed by connecting, e.g., serially connecting, several individual batteries. For clarity, individual batteries will be referred to herein as “unit batteries,” and assemblies of unit batteries connected in series, parallel, or a combination thereof, will be referred to as “battery modules”.
In a battery module each of the respective unit batteries may include an electrode assembly, in which a separator is interposed between a positive electrode and a negative electrode. The electrode assembly may be inserted inside a container, and a cap assembly may be attached to the container to seal the container. The cap assembly may include terminals disposed so as to extend from the inside to the outside of the container, which are electrically connected to the positive and negative electrodes.
Unit batteries may be arranged to alternate positive and negative terminals, such that a positive terminal of a first unit battery may be disposed adjacent to a negative terminal of an adjacent second unit battery. Conductors may be mounted on threaded positive and negative terminals to electrically connect adjacent unit batteries to form the battery module.
A battery module may include several unit batteries to tens of unit batteries. As the unit batteries may generate heat, in a module containing multiple unit batteries there may be a need to efficiently discharge heat generated from each unit battery. In particular, when the battery module is a large, bulk size secondary battery module for, e.g., drive motors, HEVs, electric vehicles, electric scooters, rechargeable vacuum cleaners, etc., the efficient discharge of heat may be of significant importance.
If heat emission from the battery module is not properly managed, the temperature of the battery module may increase excessively, due to heat generated by each unit battery, and the battery module, and the machine connected thereto, may malfunction.
In addition, if the internal pressure of the unit battery is increased due to excessive heat or other factors, e.g., due to a chemical reaction inside the unit battery, the external dimensions of the unit battery may become distorted. This distortion negatively affects the characteristics of the unit battery and may affect the battery module as a whole.